1. Field of the Invention
The present invention relates generally to an air feeding system for a vehicle engine equipped with a supercharger, and more particularly, to a system for feeding air to a cylinder of an internal combustion engine equipped with a supercharger to be used in a vehicle, in which an air cleaner, a supercharger and an engine body are successively interconnected through a plurality of portions of an inlet passage.
2. Description of the Prior Art
In one example of an internal combustion engine equipped with an engine-driven supercharger, an air cleaner, a throttle valve and the engine-driven supercharger are disposed in an inlet passage from the upstream portion to the downstream portion thereof, as disclosed in the Japanese patent application published before examination under publication number 62-178730. The inlet passage is ordinarily provided with a bypass extending from a portion of the inlet passage downstream of the throttle valve to detour or bypass the supercharger. An air relief valve is also provided for the bypass to control air flow in the bypass so as to adjust intake air mass flow supplied to the supercharger. Further, an intercooler is usually disposed between the supercharger and an intake manifold connected to an engine body of the engine for cooling intake air which is compressed by the supercharger, and for supplying same to a cylinder of the engine body.
In previously proposed vehicles each employing the internal combustion engine equipped with the engine-driven supercharger, usually the air cleaner, supercharger and intercooler are arranged to be positioned on the same side of the engine body of the engine in an engine room with the intention of having an air feeding system, which comprises an inlet passage and the air cleaner, supercharger and intercooler interconnected through portions of the inlet passage, reduced in volume. Such an arrangement is shown in the Japanese patent application published before examination under publication number 63-93623. In such a case, it is desired that the air cleaner which is considerably large in volume is usually positioned at a front portion of the engine room so as to introduce fresh cool air into the inlet passage and thereby to improve air charging efficiency in the cylinder of the engine body. In addition, the intercooler which requires a relatively large space to be placed therein is also positioned at the front portion of the engine room so as to improve the cooling effect of the intake air compressed by the supercharger. It is also desired that the supercharger which is considerably large in volume is positioned at a portion of the inlet passage downstream from the throttle valve so as to effectively suppress noise caused by intake air flowing through the supercharger to get away from portions of the inlet passage upstream of the supercharger. It is further desired that the throttle valve is positioned to be close to a cabin so as to be smoothly controlled by a wire which transmits movements of an accelerating pedal disposed in the cabin to the throttle valve.
However, in practice, it is quite difficult to have such an air feeding system in which the air cleaner, supercharger and intercooler are positioned on the same side of the engine body in the engine room in the manner that each of the above described desires is satisfied. Further, even if the above mentioned air feeding system is obtained under a hood covering the engine room in some way, the inlet passage must be formed to have a number of bent portions and therefore resistance against intake air flow through the inlet passage must be undesirably increased thereby reducing power of the engine. Especially, in the case of a vehicle employing a V-type engine which is usually accompanied with relatively small spaces formed on both sides thereof in an engine room, the problems mentioned above become more conspicuous.
In the field of the V-type engine, there has been proposed an air feeding system in which the engine-driven supercharger is disposed between a pair of cylinder banks forming V-shaped front and rear ends under a hood covering an engine room, as shown in the Japanese utility model application published before examination under publication number 61-1624. However, when the air feeding system thus proposed is adopted for the V-type engine, the size of the engine is increased in height and therefore a general desire of reducing the height of the hood covering the engine room cannot be satisfied.